Introduction to SAT II Physics

A piano mover pushes on a piano with a force of 100 N, moving it 9 m in 12 s. With how much power

does the piano mover push?

Power is a measure of the amount of work done in a given time period. First we need to calculate
how much work the piano mover does, and then we divide that quantity by the amount of time the
work takes.

Be careful not to confuse the symbol for watts, W, with the symbol for work, W.

Instantaneous Power

Sometimes we may want to know the instantaneous power of an engine or person, the amount of
power output by that person at any given instant. In such cases, there is no value for to draw
upon. However, when a steady force is applied to an object, the change in the amount of work
done on the object is the product of the force and the change in that object’s displacement. Bearing
this in mind, we can express power in terms of force and velocity:

Key Formulas

Work

Work Done

by Gravity

Kinetic

Energy

Work-

Energy

Theorem

Potential

Energy

Gravitational

Potential

Energy